The present invention relates generally to the field of vibration welding fabrics to substrates, such as is the case with fabric covered panels. More particularly, the present invention is related to a method for manufacturing carpet/fabric panels without the use of energy directors such as carpet engaging pins.
Many articles, such as automobile car door panels, typically are formed of a thermoplastic substrate that can be formed using injection molding, thermoforming, extrusion or vacuum forming. It is often desired to cover sections of this panel with another material such as a synthetic fiber carpet or a fabric or another material. This covering can be for aesthetic and/or functional purposes.
Traditional production processes used for bonding materials to door panels require additional consumables. These can include, but are not limited to, glue, staples, clips and other mechanical means. Such additional consumables tend to affect the re-cyclability of the thermoplastic substrates to which the carpet/fabrics are bonded, may not provide aesthetically pleasing results and may not provide adequate bonding or attachment.
Other known bonding processes include linear or orbital vibration welding. U.S. Pat. Nos. 5,026,445 and 5,468,335, for example, disclose a thermoplastic substrate and a synthetic fiber carpet bonded together by a vibration welder generating frictional heat at an interface between the substrate and an underlying carpet. Specifically, both U.S. Pat. Nos. 5,026,445 and 5,468,335 disclose the use of a platen having a pattern of closely spaced pins. These pins are capable of penetrating the loft of a carpet and serve as energy directors with which a backing layer of the carpet can be welded to the thermoplastic substrate at the regions opposite to the pins.
The above-mentioned patents disclose welding processes that make use of the fact that thermoplastics will remelt with the application of heat and then resolidify once the heating ceases. These processes do not require mechanical devices for the attachment of the pieces to be welded.
One of the difficulties incurred in using the above-described welding processes is that they require the carpet layer to be subjected to localized contact either with ultrasonic horns or engaging pins used in vibration welding as taught by U.S. Pat. Nos. 5,026,445 5,468,335. This localized contact, though indispensable for the disclosed processes, causes a marking or formation of telltale pin dents in the carpet welded to the plastic panel. To eliminate the dents it is then necessary to brush, comb or otherwise smooth out the effects of these processes upon the carpet surface. Another difficulty in using the welding apparatus described in these patent is that the manufacture of platens with pins involves an expense.
Other bonding processes have been developed which significantly improve on the processes disclosed in U.S. Pat. Nos. 5,026,445 and 5,468,335. These improved processes are set forth in U.S. Pat. Nos. 6,066,217 and 6,227,275, which are commonly owned with the present application, and which are fully incorporated by reference herein. One of the processes disclosed in U.S. Pat. Nos. 6,066,217 and 6,227,275 involves providing a thermoplastic substrate and a carpet with a thermoplastic backing. Either the substrate or the backing layer of the carpet is textured with a plurality of distributed tiny raised regions. Where these regions are positioned, bonding regions are formed at an interface between the backing layer and the substrate""s outer surface, such preferential bonding regions being produced from the vibration welding. These bonding regions are widely distributed so as to form distinct and extensively distributed bonded zones. The result is a well bonded fabric.
However, while the above described process disclosed in U.S. Pat. Nos. 6,066,217 and 6,227,275 provides excellent results, there is no teaching as to how the raised regions provided on either the substrate or the backing layer are formed. The present invention is specifically directed to a novel method for forming the raised regions on the backing layer of the carpet. Moreover, as U.S. Pat. Nos. 6,066,217 and 6,227,275 teach that locating the raised regions on the substrate is preferred and only briefly mentions that the raised regions may be located on the backing layer, there is no suggestion of the below described novel method therein, and in fact the novel method could not be used in connection with the preferred arrangement disclosed in U.S. Pat. Nos. 6,066,217 and 6,227,275 wherein the raised regions are provided on the substrate.
With a vibration welding technique in accordance with the present invention there is no localized pin contact with the fabric and, therefore, there are no markings or pin dents to be removed or brushed out. The term fabric as used herein includes heavy fabrics such as carpets as well as lighter weight and thinner fabrics which, when used with this invention, are backed by a usually thicker backing layer. The fabric may be a woven or non-woven material.
With the welding of a fabric in accordance with the invention, the fabric is virtually unaffected from a visual standpoint and no further steps need to be taken to restore the appearance of the fabric.
Instead of relying upon the use of a fixture having a specified pin structure, with the pins selected to penetrate the piles of a carpet, to produce localized contact between the fabric and the substrate, both the substrate and the fabric are transformed so as to be a part of the welding structure. This is achieved with one method according to the invention by providing a flexible fabric having a backing layer and creating a plurality of distributed raised regions on the backing layer by heating the backing layer in order to soften it and then pressing a die into the backing layer to cause the portions of the softened backing layer to flow into recesses provided in the die to form the raised regions. The backing layer may be heated and pressed with the die in discrete steps, or in a single step where the die itself is heated. The die may comprise a calendaring roller having a continuous outer surface in which are provided the recesses. The backing layer may comprise a single thermoplastic layer of material or may comprise a plurality of layers of material joined together, at least the outermost layer being formed from a thermoplastic material. The raised regions may be uniformly sized, shaped and/or spaced or may be randomly sized, shaped and/or spaced.
The flexible fabric is disposed on the substrate so that the bottom surface backing layer (i.e., the surface with the raised regions) is in intimate pressurized contact with the substrate at an interface which extends over an effectively continuous and substantial portion of the bottom surface of the fabric.
The fabric and substrate are then displaced relative to one another while in intimate pressurized surface contact until the raised regions which are in contact with the substrate are softened to cause either an interpenetration or fusion of softened raised regions with the substrate. When the displacing step is stopped the softened zones harden and form a large number of distributed bonds between the fabric and the substrate.
With a method of this invention various materials can be vibration welded to a thermoplastic substrate. Thus the material can be a carpet which has a backing layer. The carpet can have regions (i.e. between the raised regions) that may not necessarily be fused with the substrate but because of the distributed nature of the raised regions, excellent bonding is achieved.
Because the entire surface of the backing layer is not required to be melted with a method of this invention, but rather only the localized areas of the raised regions are required to be melted, bonding can be achieved over a larger area with a lower input of energy. Similarly, higher clamping forces can be locally applied to the raised areas, thereby generating more localized heating at the welding interface. Moreover, a more even distribution of bonding is achieved because the energy is focused only on the raised regions of the backing layer. Furthermore, a wider variety of carpet materials can be welded since the backing layer can be independent of the fabric and can be compatible with the thermoplastic substrate.
The material can be a flexible fabric with a backing layer or even a vinyl layer with either sufficient thickness to be directly welded to the substrate or with an intermediate backing layer (so long as either the vinyl layer or the backing layer if one is provided has created thereon raised portions as described above). The term fabric as used herein, therefore, includes such materials as a heavy fabric or carpet, vinyl with a backing layer and other similar thin materials that can be directly vibration welded to thermoplastic substrates in accordance with the invention and in which raised portions can be formed using the method of the present invention.
When a fabric is vibration welded to a thermoplastic door panel a large selection of colors and patterns can be employed for an enhancement in the appearance of the door panel.
The scope of the present invention includes the method for vibration or orbital welding of a carpet/fabric to a three dimensionally contoured substrate such as commonly found on car door panels and the like. Such welding involves placing the substrate and fabric between a pair of similarly three dimensionally contoured platens whose active surfaces are substantially parallel and without pins. The term vibration welding as used herein includes orbital welding.
Another feature of the invention involves the use of tooling that can be more easily prepared for a vibration welding application. Thus with tooling in accordance with the invention upper and lower tools are provide with typically the lower tool being moveable to engage the upper tool with pressure while the substrate and fabric workpieces are between them. The lower tool has a workpiece engaging surface shaped to match that of the contour of the substrate workpiece. This surface is provided with an appropriate amount of friction to grip the fabric without slipping.
The lower tool is preferably segmented with segments having surfaces adapted to conform to the contour of the back of the substrate that is to be bonded to the fabric. The segments are adjustable so as to assure appropriate surface wide pressure contact for area wide bonding between the fabric and the thermoplastic substrate. If necessary, the contacting surfaces of the segments are provided with enhanced friction to avoid slipping of the substrate.
With vibration welding tools in accordance with the invention the use of pins as required by the prior art can thus be advantageously avoided.
It is therefore an object of this invention to provide an improved method for vibration welding of a fabric to a substrate while overcoming the drawbacks of the above-described prior art.
Another object of the invention is to provide a method of manufacturing soft material covered panels using vibration welding for bonding a carpet or other fabric to a thermoplastic substrate without damaging the decorative surface of the fabric.
Another object is the invention is to provide a vibration welding method for bonding an interstitial surface of a carpet having a backing layer with a thermoplastic substrate.
Still another object of the invention is to provide a vibration welding method for bonding a fabric having a thermoplastic substrate having raised regions formed thereon to a thermoplastic substrate surface.
Yet another object of the invention is to provide a suitable method for forming raised regions on the thermoplastic backing layer of a fabric.
Yet another object of the invention is to provide a tool for vibration welding of fabrics to thermoplastic substrates of different contours.
The invention and its particular features and advantages will become more apparent from the following detailed description considered with reference to the accompanying drawings.